82 ROLAND FISCHER 



keratin, around 80% or more of which is in the form of cystine. We were in- 

 terested therefore in determining the possible influence of this sulphur on the 

 affinity of compounds for wool. 



I performed some experiments with what we call the spectrophotometric 

 method; that is, we measured the absolute affinity of a compound to wool and 

 compared it then with the relative affinity obtained by the weight increase 

 method just mentioned. Using crystal violet as test substance, the determina- 

 tion of the absolute affinity to intact wool showed us that the wool does not 

 take up any dyestuff at all: experimental conditions: 24°C, pH = 6.3, 0.2. gm. 

 dyestuff, 50 cc. of water, 1 gm. of wool, 10 min. However, 1 gm. of wool which 

 has been pretreated with 0.15N Na 2 C0 3 at 80°C. for 3 hours, (H.D. = highly 

 degraded wool) took up 247 of crystal violet, that is 0.15 y per mg. H.D. wool- 

 nitrogen. 



If we block the SH-groups of H.D.-wool by a "Salyrgan"-treatment, this 

 wool will take up only 0.08 y crystal violet per mg. H.D. wool-nitrogen under 

 otherwise similar experimental conditions. However, we found afterwards that 

 any treatment of H.D.-wool which diminishes its base-attracting groups will 

 diminish its affinity for cationic compounds. 



Dr. Morales: I should think that if binding is unaffected by blocking the 

 disulphide linkages then you are obligated to try this on another protein since 

 that certainly was one thing that was characteristic. I would think that myo- 

 sin or something of the same fibrous series would be it. 



The things that I started to ask you were these. Experimentally, how do you 

 measure the binding and, secondly, your explanation of how these things bind 

 escaped me — I mean, what kind of forces you thought they were. 



Dr. Fischer: The affinity in those experiments which give relative values 

 is measured on a weight increase basis. One gm. of wool is brought to constant 

 weight — accuracy up to the fourth decimal point — over calcium chloride. A 

 "Grammatic" balance and weighing times of 20 seconds are used for each wool 

 sample under standardized conditions. There are always 2 "air"-controls and 

 one "water"-control in a series of 5 wool samples. At 90°C. and in 10 minutes 

 the affinity to wool of 0.2 gm. of substance is measured in 50 cc. of distilled 

 water at pH 5.2, which is very near to the pH of the wool. Then the wools are 

 rinsed three times with water at room temperature, pre-dried in an oven at 

 50-60°C. for about 20 minutes and then again placed in the desiccator. After 

 3-4 days, when they reach constant weight, the affinity is calculated from the 

 weight increase. 



If we measure the absolute affinity of a compound, then we submerge one 

 gram of wool into a solution of 0.2 gm. of substance in 50 cc. of water and soak 

 the wool there for 10 minutes. There is no rinsing with water but direct spec- 

 trophotometry- determination of the difference in concentration of the "dye- 

 bath" prior and after the experiment. 



